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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 28 May 2011 by dana1981

The Australian government established a Climate Commission which recently released a three chapter report entitled The Critical Decade. The first chapter of the report, which we will examine in this post, summarizes the current state of climate science observational data. But first, a statement in the introduction is worth quoting:

"Over the past two or three years, the science of climate change has become a more widely contested issue in the public and political spheres. Climate science is now being debated outside of the normal discussion and debate that occurs within the peer-reviewed scientific literature in the normal course of research. It is being attacked in the media by many with no credentials in the field. The questioning of the Intergovernmental Panel on Climate Change (IPCC), the “climategate” incident based on hacked emails in the UK, and attempts to intimidate climate scientists have added to the confusion in the public about the veracity of climate science."

We at Skeptical Science have documented many such attacks on climate science by individuals with no climate credentials, who misrepresent scientific research, and attempt to sow doubt in the minds of the general public through non-scientific issues like Climategate. But while these introductory comments are worth highlighting, let's move on to the scientific content.

The report is based on the IPCC Fourth Assessment Report (2007) as well as several other more recent studies. Skeptical Science readers will already be familiar with much of the information in the first chapter, but it nevertheless provides a useful summary of recent climate research. The main conclusions of Chapter 1 are as follows:

The average air temperature at the Earth’s surface continues on an upward trajectory at a rate of 0.17°C per decade over the past three decades.

The temperature of the upper 700 meters of the ocean continues to increase, with most of the excess heat generated by the growing energy imbalance at the Earth’s surface stored in this compartment of the system.

The alkalinity of the ocean is decreasing steadily as a result of acidification by anthropogenic CO2 emissions.

Recent observations confirm net loss of ice from the Greenland and West Antarctic ice sheets; the extent of Arctic sea ice cover continues on a long-term downward trend. Most land-based glaciers and ice caps are in retreat.

Sea-level has risen at a higher rate over the past two decades, consistent with ocean warming and an increasing contribution from the large polar ice sheets.

The biosphere is responding in a consistent way to a warming Earth, with observed changes in gene pools, species ranges, timing of biological patterns and ecosystem dynamics.

The report notes that the past decade (2001-2010) was the hottest on record, 0.46°C above the 1961-1990 average. It also contains many illuminating figures, including this one showing that Arctic sea ice is declining far faster than IPCC models projected, currently approximately 40 years ahead of schedule.

Chapter 1 proceeds to discuss the various signals of a changing Australian climate in the biosphere, including mammalian migrations to higher elevations, earlier arrival and later departure times of migratory birds, and the increase in bleaching events on the Great Barrier Reef (GBR). There have been eight mass bleaching events on the GBR since 1979 with no known such events prior to that date. The report goes on to discuss the potential causes of the observed climate change:

There is no credible evidence that changes in incoming solar radiation can be the cause of the current warming trend.

Neither multi-decadal or century-scale patterns of natural variability, such as the Medieval Warm Period, nor shorter term patterns of variability, such as ENSO (El Niño-Southern Oscillation) or the North Atlantic Oscillation, can explain the globally coherent warming trend observed since the middle of the 20th century.

There is a very large body of internally consistent observations, experiments, analyses, and physical theory that points to the increasing atmospheric concentration of greenhouse gases, with carbon dioxide (CO2) the most important, as the ultimate cause for the observed warming.

Improved understanding of the sensitivity of the climate system to the increasing atmospheric CO2 concentration has provided further evidence of its role in the current warming trend, and provided more confidence in projections of the level of future warming.

"An analysis of the transition of the Earth from the last ice age to the Holocene, which infers climate sensitivity from the observed change in temperature and the corresponding changes in the factors that influence radiative forcing, also estimates a value of about 3°C (Hansen et al. 2008). Much of the uncertainty on the magnitude of climate sensitivity is associated with the direction and strength of cloud feedbacks. Recent observational evidence from short-term variations in clouds suggests that short-term cloud feedbacks are positive, reinforcing the warming, consistent with the current model-based estimates of cloud feedbacks (Clement et al. 2009; Dessler 2010).

A recent model study comparing the relative importance of various greenhouse gases for the climate estimates a sensitivity of approximately 4°C for a doubling of CO2 (Lacis et al. 2010). In addition, the study points to the importance of CO2 as the principal “control knob” governing Earth’s surface temperature."

It's worth noting that while Hansen et al. find paleoclimate evidence for a short-term climate sensitivity of 3°C for doubled atmospheric CO2, they also find that when including slow-acting feedbacks, the long-term sensitivity is closer to 6°C. Next up is a discussion of how the carbon cycle is changing:

Despite the dip in human emissions of greenhouse gases in 2009 due to the Global Financial Crisis, emissions continue on a strong upward trend, on average tracking near the top of the family of IPCC emission scenarios.

Ocean and land carbon sinks, which together take up more than half of the human emissions of CO2, appear to be holding their proportional strengths compared to emissions, although some recent evidence questions this conclusion and suggests a loss of efficiency in these natural sinks over the past 60 years.

If global average temperature rises significantly above 2°C (relative to pre-industrial), there is an increasing risk of large emissions from the terrestrial biosphere, the most likely source being methane stored in permafrost in the northern high latitudes.

There is evidence that the efficiency of natural carbon sinks is declining, particularly in the Southern Ocean, but this possibility remains highly uncertain and controversial. Thus far natural carbon sinks have kept pace with us, absorbing approximately 57% of human emissions since 1958, but there is of course a limit to their storage capacity.

As the planet continues to warm, approaching the 2°C danger limit, not only is there an increasing risk that these natural carbon sinks will become saturated, but potentially significant releases from other carbon sources (methane beneath permafrost, methane hydrates stored under the sea floor, organic material stored in tropical peat bogs, etc.) becomes increasingly likely.

The final section in Chapter 1 discusses the certainty of our knowledge of climate change:

The IPCC’s Fourth Assessment Report has been intensively and exhaustively scrutinised and is virtually error-free.

The Earth is warming on a multi-decadal to century timescale, and at a very fast rate by geological standards. There is no doubt about this statement.

Human emissions of greenhouse gases – and CO2 is the most important of these gases – is the primary factor triggering observed climate change since at least the mid 20th century. The IPCC AR4 (2007a) report attached 90% certainty to that statement; research over the past few years has strengthened our confidence in this statement even more.

Many uncertainties surround projections of the particular risks that climate change poses for human societies and natural and managed ecosystems, especially at smaller spatial scales. However, our current level of understanding provides some useful insights: (i) some social, economic and environmental impacts are already observable from the current level of climate change; (ii) the number and magnitude of climate risks will rise as the climate warms further.

The report notes that some significant uncertainties remain, such as the exact responses of the Greenland and Antarctic ice sheets, and the hydrological cycle, to the continuing warming of the planet. But the report also hammers home a key point that we wish "skeptics" would take to heart:

"These uncertainties, however, in no way diminish our confidence in the observation that the Earth is warming and in our assessment that human emissions of greenhouse gases are the primary reason for this warming."

"Despite these seemingly daunting uncertainties, a number of social, economic and environmental impacts can be observed that are consistent with what is anticipated from the current level of climate change. The number and magnitude of climate-related risks will rise considerably as the climate warms towards 2°C above the preindustrial level; and above the 2°C guardrail, the risks may rise dramatically"

In short, despite the uncertainties, the scientific evidence is clear on the main points that humans are causing dangerous global warming. It's also important to note that uncertainties can go either way, and the consequences of climate change are just as likely to be more damaging than we expect as less. Uncertainty is not our friend.

In Parts 2 and 3 we will examine the report's chapters on risks associated with climate change and implications of the science for emissions reductions.

Comments

Excellent summary of information that is valuable to have at ready access!

However there is an error in the statement:
"The alkalinity of the ocean is decreasing steadily as a result of acidification by anthropogenic CO2 emissions."

Rising atmospheric CO2 does not change the alkalinity of seawater. Rather, rising CO2 lowers the concentration ratio of carbonate ions to bicarbonate ions, while maintaining a constant alkalinity. It is the concentration of carbonate ion that is thought to most affect calcification by organisms.

Based on their wording, my guess is that they are trying to avoid the whole "it can't be acidification of the ocean's pH is >7" nonesense. "Less alkaline" gets around that, but they said "less alkalinity" instead by mistake.

MattJ - again, that's a direct quote from the report (all bullets are taken straight from the report). I suppose you're right that some people have doubts, but not informed, rational people. The report likely refers to no doubt amongst the climate science community.

the statement "Neither multi-decadal or century-scale patterns of natural variability, such as the Medieval Warm Period, nor shorter term patterns of variability, such as ENSO (El Niño-Southern Oscillation) or the North Atlantic Oscillation, can explain the globally coherent warming trend observed since the middle of the 20th century."
seems to be rather firmly established.

However the content of the report doesn't really confirm this strength. The only detailed argument presented in the report is

"The Medieval Climate Anomaly (MCA), a somewhat warmer period from about 1000 to about 1250 or 1300 AD, has sometimes been invoked to infer that the contemporary warming is nothing unusual in the Holocene and that it is thus likely due to natural variability. However, the bulk of evidence for the MCA comes from the northern hemisphere, which makes it difficult to determine whether the MCA was truly global in scale. Furthermore, a spatially explicit synthesis of all available temperature reconstructions around the globe suggests that the MCA was highly heterogeneous, even in the northern hemisphere, with globally averaged warming much below that observed over the last century (Mann et al. 2009; Figure 9). Thus, the MCA is different in magnitude and extent from contemporary warming (Figure 10)."

I don't really see how strong this argument is. IPCC has defined a scale of "likelihood" with confidence intervals : wouldn't be desirable to quantify the confidence level at which we can exclude that the current warming rate (approx 0.5 °C in 30 years) ? is it at 90 % ? at 99 % ? what is the accuracy of globally averaged warming 1000 years ago ?

Is the sentence starting "It's worth noting that while Hansen et al. find paleoclimate evidence..." about eventual near 6 °C sensitivity actually summarizing something in the report or is it additional commentary? I couldn't find it in the report looking just at the most obvious page from the context and searching for "6 °" or "6°". If it is an aside I think it's potentially misleading not to label it as such much more clearly.

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Response:

[dana1981] That's my commentary (and it's true). Everything in quotes or bullets is from the report. Everything else is from me.

Why don't we take a hard look at the latest report from Messrs Flannery, Steffan and Karoly et al - three vocal advocates for the AGW position with a lot of professional skin in the game:

"1) The average air temperature at the Earth’s surface continues on an upward trajectory at a rate of 0.17°C per decade over the past three decades."

Note that they don't mention the last decade, where the warming has flattened by all measures.

"2) The temperature of the upper 700 meters of the ocean continues to increase, with most of the excess heat generated by the growing energy imbalance at the Earth’s surface stored in this compartment of the system."

"A growing energy imbalance at the surface stored in this compartment of the system." A carefully compartmentalized description indeed. What about the flattening OHC for the last 7-8 years in the top 0-700m and the overall TOA imbalance?

"3) The alkalinity of the ocean is decreasing steadily as a result of acidification by anthropogenic CO2 emissions."

It seems that the latest argument is that heat is transported to the 700-2000m depths by a yet undescribed short term deep mixing mechanism - but CO2 does not travel with it, otherwise the pH effect would be infinitesimal.

"4) Recent observations confirm net loss of ice from the Greenland and West Antarctic ice sheets; the extent of Arctic sea ice cover continues on a long-term downward trend. Most land-based glaciers and ice caps are in retreat."

With 90% of the planet's ice in Antarctica, should not the vast majority in East Antarctica be mentioned?

"5) Sea-level has risen at a higher rate over the past two decades, consistent with ocean warming and an increasing contribution from the large polar ice sheets."

Last time I looked, Jason 1 and 2 were giving a 1.7-2.0mm/year SLR globally. If the ice melt is an increasing contribution then steric rise is a decreasing contribution, which fits with a flattening OHC increase. By far the greater energy is absorbed in a 1mm steric rise than a 1mm ice melt rise.

"6) The biosphere is responding in a consistent way to a warming Earth, with observed changes in gene pools, species ranges, timing of biological patterns and ecosystem dynamics."

Evidence of warming is not evidence of AGW.

"7) The report notes that the past decade (2001-2010) was the hottest on record, 0.46°C above the 1961-1990 average."

If warming has flattened and approached a plateau, this decade will be 'Hotter' than the last decade and the last decade 'Hotter' than the decade before that. Even if warming has stopped, this decade will remain the 'hottest on record'.

And as a general comment, Jim Hansen (a major IPCC AR4 author and seminal AGW theorist) in his latest effort "Earth's Energy Imbalance and Inplications" suggests that the 2005-10 planetary imbalance has reduced from a pre-2005 estimate of 0.9W/sq.m to 0.59W/sq.m. His reasons are a prolonged Solar Minimum, largely underestimated Aerosol cooling, and a delayed rebound effect from Mt Pinitubo aerosols.

While his reasons are debatable, he has abandoned the 'its there but be can't measure it' argument for maintaining the 0.9W/sq.m imbalance which in theory should be increasing since 2005 due to greater CO2GHG concentrations in the atmosphere and a growing induced positive WV and ice albedo feedback.

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Response:

[dana1981] I don't have the time to respond to this entire Gish Gallop, but you're cherrypicking. The last 30 years includes the last 10 years.

@Ken Lambert "4) Recent observations confirm net loss of ice from the Greenland and West Antarctic ice sheets; the extent of Arctic sea ice cover continues on a long-term downward trend. Most land-based glaciers and ice caps are in retreat."

With 90% of the planet's ice in Antarctica, should not the vast majority in East Antarctica be mentioned?

Why would you not mention that the Antarctic ice sheet as a whole is losing mass?

Rhetorical question, of course. You ignore the big picture because anomaly hunting and cherry picking is what deniers do.

newcrusader:
I am not convinced that the Arctic will be ice free in late summer by 2030.
I do think this year will have a very low min...my prediction is approx 3.5 using Jaxa data.

The particulates coming from China are playing a very heavy toll on sea ice.

The last paper that I have read concerning the Arctic was by Schmidt/Lindall etal where they showed that soot etc was more responsable for the decline than co2.

The last time that Arctic Ice was flowing out as it is now was in 1944, the year that the St Roch sailed the deepwater Northwest Passage. You can buy the book from the museum in Vancouver that has Capt Larson's log in it where he describes ice conditions on that journey.

Will we have a rebound in ice in years to come? My gut instinct, which is worth nothing scientific says yes.

Time will tell if my gut is right. I think that pollution in China will become such a social issue that they will take known steps to curb it. I think they are very foolish right now to be using their country as a dumping ground when the teck is well proven with scrubbers etc to virtually eliminate particulate pollution from burning coal.

sorry to disagree with you- but the 1944 'story' has never been scientifically verified. I also disagree with you that there will not be an ice free arctic by 2030- by that time C02 will have reached 425-430ppm- and global temperatures will have risen another 1 degree C.

What you are saying here, basically flies against what Hansen and Sato have said (which has been very accurate)

The IPCC said ice late summer would occur around '2065' and a sea level rise under a foot. (this has recently been changed- to the higher level- 3 feet---

Since the huge melt in 2007, 2008, and last year- and the thin ice now in the arctic 1 & 2 years, and disappearing thick ice, your predictions are totally different then what NASA, the NOAA and the NSIDC predict.

newscrusader @19, doubting the Royal Canadian Mounted Police when they claim to have transited the North West Passage is unwarranted. On the other hand, Camburn's suggestions that ice conditions now match those of 1944 when in recent years when transits have now become common place, even by cruise liners, and two yachts circumnavigated the globe through the north east passage and north west passage in a single season in 2010 are ridiculous.

unless there is photographic evidence showing that ice melt comes close to the years 2006-2010, and the minim of 2007, The highly esteemed RCMP report as eyewitnesses to an ice free passage can be taken for what it is worth. Sorry.

I guess I like to see absolute empirical evidence. In 1944 there was obviously no Satellites to preserve such an event. It seems improbable in 1944 when C02 levels where still below 300ppm.

Nonetheless some kind of anomaly cannot be totally dismissed- misunderstood or misinterpreted perhaps.

Anyone who really wants to know the facts about crossings of the Northwest passage (as Tom Curtis has noted), can easily discover the truth and will notice the difference between previous trips and those that are currently undertaken :

In 1944, St. Roch returned to Vancouver via the more northerly route of the Northwest Passage, making her run in 86 days.

The RCMP ship was the 104-foot, schooner-rigged St. Roch, which was specially built for resisting the crushing pressures of sea ice that would destroy her.
Although the return trip to Vancouver presented certain navigational difficulties, these were far less life-threatening than the ones encountered on the more southerly route. It took only 86 days to sail from Halifax to Vancouver. The route taken, through Parry Channel, and then Prince of Wales Strait at its western end, will most certainly be the one first used by commercial shipping as global warming accelerates the thinning of the Arctic ice cover.

1st commercial ship sails through Northwest Passage.
Rayes, who was on the vessel during its trip through the Northwest Passage, said the company informed the coast guard, which put an icebreaker on standby.
"They were ready to be there for us if we called them, but I didn't see one cube of ice," he said.
"They were informed about our presence [and] they were ready to give us the support needed. However, since there was no ice whatsoever, the service was not needed, we didn't call for it."

I pointed out that the report highlighted the Greenland and West Antarctic ice loss without mentioning the majority of the planet's ice in East Antarctica. An AGW cherry pick par excellence I would have thought.

Last time I looked, East Antarctica was neutral or slightly increasing ice mass, and the overall Antarctic was a slight loss (Camburn might correct me on this if I am not right up to date). This overall loss equates to a 0.12mm contribution to the global SLR which is officially 3.1mm/year, but Jason 1 and 2 show 1.7-2.0 mm/year. Global tide gauges are showing even less than this.

Overall global ice melt is very small contribution to the net global energy imbalance even when Hansen's smaller imbalance is taken into account.

Camburn @18, can you provide a clearer reference to Schmidt Lindall et al. I can find no relevant paper from them in a search of google scholar. What I did find was a paper by Screen and Simmonds (2010), who write:

"Here we show that the Arctic warming is strongest at the surface during most of the year and is primarily consistent with reductions in sea ice cover. Changes in cloud cover, in contrast, have not contributed strongly to recent warming. Increases in atmospheric water vapour content, partly in response to reduced sea ice cover, may have enhanced warming in the lower part of the
atmosphere during summer and early autumn. We conclude that
diminishing sea ice has had a leading role in recent Arctic temperature amplification. The findings reinforce suggestions that strong positive ice–temperature feedbacks have emerged in the Arctic, increasing the chances of further rapid warming and sea ice loss, and will probably affect polar ecosystems, ice-sheet mass balance and human activities in the Arctic."

(My emphasis)

Black carbon is, it appears, hardly worth a mention in the Arctic. That is not surprising given the large distance to the primary sources (India, China) and the low residence time in the atmosphere of black carbon.

Ken Lambert @26, yes cherry picking because you continue to insist or reporting only the recent short term trend when the duration of that trend is no where near long enough to determine if it is a genuine change in the long term trend, or merely a short term fluctuation.

Labelling of the various denier cherry picks and gish gallops as cherry picks and gish gallops may have become uncomfortably frequent, but the solution lies entirely in denier hands. Stop producing them and we will no longer have to call you on it.

Camburn, the paper you are looking for is Chen 2009. There is some small ice loss in East Antarctica but as everyone points out, the is net ice loss for all of Antarctica and it appears to be accelerating.

Tom Curtis @ 27:
It was published in science, the paper by Schmidt/Lindell.

I will see if I can find a link.

As far as East Antarctica, where over 90% of the worlds ice is, there is no conclusive evidence that the ice in increasing, nor is there evidence that the ice is decreasing. It appears to be static at this time.

Apart from the point raised by boba 10960, I have only one minor quibble with this informative article, which states … “humans are causing dangerous global warming”. I would argue that the past tense would be more accurate …”humans have caused” or … “humans continue causing dangerous global warming”.

Humans have now emitted sufficient greenhouse gases to initiate methane emissions from onshore permafrost and offshore clathrates, both entering the atmosphere as CH4. Those emissions were 4 and 8 tonnes per annum in 2005 and neither the melting of ice or the magnitude of their release is going to decrease. Both are predicted to increase –Shakhova et al (2010).

Hansen et al (2011) warn that as a result of anthropogenic emissions and these slow emissions, polar temperature can be expected to more rapidly reduce sea ice and increase Arctic amplification. This is predicted to result in decadal doubling of ice loss from the Greenland Ice Sheet, initiating its eventual collapse and raising sea level by 5m before 2100.

Hansen goes further. He expresses the view that as ocean warming continues it will result in them releasing CO2 and those releases increasing in magnitude such that the net ability of oceans to absorb CO2 reduces. It should be noted that this outcome is expected to occur during a period when human emission of greenhouse gases can be expected to increase.

It seems to me that these developments provide sufficient pointers to the fact that humans have been causing dangerous global warming for well over a decade and are continuing to do so, irrespective of consequences which are dire indeed!

As discussed here, the balance of evidence suggests that East Antarctica is loosing ice, though at a slower rate. Even if it was not loosing ice, however, one wonders at the relevance of a specific mention. The volume of ice from just Greenland and West Antarctica is more than sufficient to drive sea levels many meters higher, and projected accelerations of the rate of loss in these two regions are sufficient to drive sea level gains of from 1 to 2 meters in the coming century, with potential but contentious rises as high as 6 meters.

Given these facts, is it really so urgent to advise the Australian public that East Antarctica is not expected to contribute significantly to the deluge for another century or so?

(On a side note, you will note the difference in word count between a rebutall of Lamert's inane suggestion and that needed to make it. It is that difference which makes his post a clear Gish gallop.)

Ken Lambert. According to my Data UAH shows a warming trend of +0.0174 degrees per year for the last decade (2000-2010), RSS shows a warming trend of +0.009 degrees per year for this same period. GISS shows a warming trend of +0.015 degrees per year for the last decade. Oddly, the CRU (the ones the Contrarians accuse of "doctoring" climate data) show only a +0.005 degree warming per year for 2000-2010. Either way, there is *no* real flattening of the warming trend-especially when you take into account the decade of deep solar minimum that we've been through. Also, why were 8 of the 10 hottest years in this decade, if the warming trend had leveled off?

Tom:
From your quote on the link embedded:
"This evidence clearly supports the view that ice loss from West Antarctica significantly excedes that from East Antarctica, but is ambiguous about whether East Antarctica is loosing ice. On balance, it is probably loosing ice, but the GRACE experiment may well be overestimating the rate of loss"

When you read current literature about East Antarctica, no one is claiming that it is loosing ice. They all admit, as you do, that there is no trend plus or minus.

JMurphy@24:
The passage that the St Roch sailed has not been sailed since. The ships are so far using the southern route in the NWP.

The northern route that the St Roch sailed is still closed. I can once again only suggest that you contact the museum in Vancouver to get the book that has the logs of Capt Larson in them. I have asked for permission to post them online, but so far it has not been granted.

"In Parts 2 and 3 we will examine the report's chapters on risks associated with climate change and implications of the science for emissions reductions."

Should be interesting..will you be explaining how a tax on CO2 in Australia will make Australian climate "better" in the future when the other industrial "polluters" dont reduce their own CO2 emissions.

Flannery: Just let me finish and say this. If the world as a whole cut all emissions tomorrow the average temperature of the planet is not going to drop in several hundred years, perhaps as much as a thousand years because the system is overburdened with CO2 that has to be absorbed and that only happens slowly.

Quote"It's also important to note that uncertainties can go either way, and the consequences of climate change are just as likely to be more damaging than we expect as less. Uncertainty is not our friend."

Translated..it might not be as bad as 99% of the stories in the media portray..
I am not sure why a lot of the posters on this excellent site really worry so much about the science being misrepresented or not..
We are getting a CO2 tax..which is exactly what you all wanted..!!
We will probably get emissions trading..which is exactly what you wanted right.?
The majority of the media never question any statement by anyone rightly or wrongly trying to link absolutely anything on earth to Human created CO2..which is exactly what you want right..?
And..who could have predicted the Orwellian term "Minister for Climate Change"..ever being created..You must be happy with that as well. ??
And last but not least..all the political parties support CAGW..at different extremes of course..
CAGW...has won.!!
Relax.. : )

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Response:

[DB] "Translated..it might not be as bad as 99% of the stories in the media portray.."

According to my Data UAH shows a warming trend of +0.0174 degrees per year for the last decade (2000-2010), RSS shows a warming trend of +0.009 degrees per year for this same period. GISS shows a warming trend of +0.015 degrees per year for the last decade. Oddly, the CRU (the ones the Contrarians accuse of "doctoring" climate data) show only a +0.005 degree warming per year for 2000-2010.

I'd imagine the error bars on each of those encompass the point estimate for the trend over the previous 20-30 years, too.

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Response:

[DB] Certainly, one could imagine it. But that would be unnecessary, as the actual analysis has already been done:

Note the error bars do not include zero in either dataset until 2001; thus, the warming since 2000 is statististically significant.

And remember that the Aughts (the decade 2001-2010) were the warmest in the instrumental record, with 2010 being tied for the warmest year on record. So, one can safely say that GW is carrying on its busy, obeying-the-laws-of-physics way, blissfully ignorant to the dissembling of those who would have us debate the existence of gravity.

What I feel some here are implying, is that the event of 1944 proves that the arctic melt minimum of 2007, but also the ice losses in 2008, 2010 where not unusual- which is basically saying that what has happened the last 6 years is nothing to be concerned about and there is no danger from CO2 and its GHG warming. Denialists? Likely.

mike williams @40, while hoping not to tread on toes for future contributions to this series, let me state the obvious.

When preparing for negotiations, you must have a clear idea of what you are prepared to concede, and what is the minimum reasonable position you will accept from other participants. If you have that in mind, then it will restrict your current strategies. It will restrict them because some actions, if taken, will prevent you ever being able to concede what in theory you are prepared to concede; or require of your negotiating partners more than the minimum reasonable position. In short, some actions will guarantee failure of any potential negotiations by changing the facts on the ground to such an extent that no reasonable negotiation can succeed.

If you are seriously intent on a negotiated solution to a problem, you will not take actions that preclude a successful negotiated solution. How is that relevant to climate change? Well, by the best available evidence, if humans do not restrict their future emissions to under one trillion tonnes of Carbon, they will face damages from climate change sufficiently severe that the continuation of our civilization (civilization, not species) is in significant doubt. So any serious negotiation must be premised on keeping total emissions under 1 trillion tonnes of carbon. Further, any serious negotiations must also be premised on equitable burdens. That means in the simplest terms equal per capita emissions quotas for all nations.

Considered in those terms, we face the unpleasant fact that the US will exceed its "carbon budget" within six years, even with no growth in emissions. Australia will do the same. It is not possible to eliminate US or Australian emissions in 6 years, and nor do they need to do so within a negotiated emissions trading framework. However, to fit within even a negotiated emissions trading solution, we need to be reducing our emissions now. Failure to do so simply is a vote for a "solution" to the problem of global warming that will not save the great barrier reef, or our economy, or (in all probability) our civilization.

Again in short, we need to take action now or we will not be in a position to comply with any global negotiated agreement. Put another way, if we don't take action now, you can be very sure that any negotiated agreement that is signed when the world's leaders finally become desperate enough to take proper action will include the requirement to buy emissions permits retrospectively for our emissions now.

The fundamental equation is this - the longer you wait to take action, the more expensive it will be to take adequate action. Waiting for negotiations to succeed will not save us one iota of that cost. But acting early may well help get an earlier negotiated agreement.

"When preparing for negotiations, you must have a clear idea of what you are prepared to concede..Again in short, we need to take action now or we will not be in a position to comply with any global negotiated agreement."

Yes Tom..I understand that...but the elephant in the corner of the room is the comments by the chief climate scientist.
Now, as many suspect, the "big polluters" like India/China/Russia/USA etc will never cut back on CO2 emission..and ,,lets face it..unless we spend more money on alternative energy systems..dirty old coal technology will still be powering alot of things in the future.
And I assume Australia will still take the moral high ground..but as you and I both know.. but only one of us will admit..if this happens..then our actions are a complete and utter waste of time.
Perhaps I have missed something in the media recently.
So my two questions are
1/Does a minority of CAGW supporters/enviromentalists etc disagree with Flannerys statements and if so can anyone please point to MSM reports/interviews etc where these views are expressed and on what technical grounds.
2/Will someone in this interesting thread be explaining how a tax on CO2 in Australia will make Australian climate "better" in the future when the other industrial "polluters" dont reduce their own CO2 emissions.
Thanks..!!

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Response:

[dana1981] This is seriously off-topic, but China is preparing to implement a carbon cap and trade system, Europe already has one in place, and the US EPA is regulating carbon emissions from large sources (and eventually we'll have a cap and trade system too, once Republicans stop blocking it). Anyway, your argument is Tragedy of the Commons - please take further discussion of the subject to that thread.

For the doubled CO2 and the 2% solar irradiance forcings, for which the direct no-feedback responses of the global surface temperature are 1.2° and 1.3°C, respectively, the ~4°C surface warming implies respective feedback factors of 3.3 and 3.0 (5).

DB, is it correct to say that the trend doesn't show any significant acceleration as well? an average 0.17°C /decade means that we would need 120 years to reach 2°C - is it the correct order of magnitude, or is a significant acceleration term expected, and when is it expected to be measurable ?

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Response:

[DB] Currently the obfuscationists deny that it is warming at all AND that what warming is occurring is natural and less-than-linear in rate. Tamino debunks that last point here and here.

As far as the warming in the pipeline, consider this and this. The thermal inertia of the oceans, coupled with the albedo changes due to the loss of the Northern Hemisphere's refridgeration system (the ongoing loss of summer sea ice in the Arctic Ocean) and increasing outgassing of GHG's from melting permafrost & clathrates mean that our descendants will have a rough go of things. Especially if we continue to refuse to do anything about it now, while our actions can still make a difference.

Time remains to have a say in our descendants future, should we demonstrate the collective will to do so. Or not.

"Hansen et al (2011) warn that as a result of anthropogenic emissions and these slow emissions, polar temperature can be expected to more rapidly reduce sea ice and increase Arctic amplification. This is predicted to result in decadal doubling of ice loss from the Greenland Ice Sheet, initiating its eventual collapse and raising sea level by 5m before 2100."

The SLR for Jason 1 and 2 is flattening to a global 1.7-2.0mm/year - down fom the official longer term trend of 3.1mm/year - and tide gauges are showing less than 1.7mm/year.

Jason 1 & 2 have been in operation since 2002. What could be explanation for this slowing of SLR when CO2GHG forcing and ice melts are supposed to be accelerating?

BTW, Hansen has just reduced the warming imbalance from roughly 0.9W/sq.m to 0.6W/sq.m for the 2005-10 period.

While his underestimated Aerosols presumably coming from 'unmeasured developing countries' is a feasible explanation, his delyed Pinitubo effect is quite preposterous. His own charts show no forcing from Pinitubo after year 2000.

The Jason 1 and 2 data taken from the homepage you linked to gives 2.3 mm/yr, not 1.7-2.0 as you say. Be carefull when quoting numbers if you care of being taken seriously.
To explain why you drop part of the record with no apparent reason is another story.